A recent study on safety and efficacy of fluvoxamine have resulted in an FDA indication for treatment of OCD in the pediatric population. We are currently conducting an efficacy trial of fluvoxamine in childhood anxiety disorders. This proposed PK study of fluvoxamine is an important opportunity to obtain PK data from a pediatric group already scheduled to receive fluvoxamine treatment. One practical application of pediatric PK data is to help guide clinical practice, and determine a rational dosing regimen for fluvoxamine in the pediatric population. Pharmacokinetics of fluvoxamine have been studied extensively in adults. In adults, PKs of fluvoxamine are non-linear, which appear dose-dependent, not time-dependent. In young adults, the steady-state half-life is between 13-15 hours. The PKs do not appear polymorphic. There is currently no PK data for fluvoxamine in the pediatric population. There is little data available regarding the relationship between fluvoxamine plasma levels and clinical response or adverse events in any age group.